Scale for photoelectric encoder

Abstract

A scale for a photoelectric encoder effectively protects the base of the scale from corrosion, rust, and flaws. The scale includes a base, a light-absorbing layer including a DLC layer formed on at least one surface of the base, and light-reflecting layers with a higher reflectance than that of the light-absorbing layer with respect to light falling within a wavelength range and formed into a grating on the light-absorbing layer.

1. A scale for a photoelectric encoder that detects reflection of light within a predetermined wavelength range, the scale comprising:
 a base; 
 a light-absorbing layer including a DLC layer formed over all surfaces of the base; and 
 a light-reflecting layer with a higher reflectance than a reflectance of the light-absorbing layer with respect to light falling within the predetermined wavelength range and formed into a grating on the light-absorbing layer. 
 
     
     
       2. The scale according to  claim 1 , wherein:
 a thickness of the DLC layer is in the range of 250 nm to 1 μm. 
 
     
     
       3. The scale according to  claim 2 , wherein:
 the light-absorbing layer has a binder layer containing at least a metal between the base and the DLC layer. 
 
     
     
       4. The scale according to  claim 2 , wherein:
 the DLC layer is formed over all surfaces of the base. 
 
     
     
       5. The scale according to  claim 2 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       6. The scale according to  claim 1 , wherein:
 the light-absorbing layer has a binder layer containing at least a metal between the base and the DLC layer. 
 
     
     
       7. The scale according to  claim 6 , wherein:
 the binder layer contains at least one of a tungsten layer, a tungsten carbide layer, a chromium layer, and a titanium layer. 
 
     
     
       8. The scale according to  claim 7 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       9. The scale according to  claim 6 , wherein:
 the binder layer contains a tungsten carbide layer, relative proportions of carbon and tungsten contained therein varying along a thickness direction of the binder layer. 
 
     
     
       10. The scale according to  claim 9 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       11. The scale according to  claim 6 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       12. The scale according to  claim 1 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       13. The scale according to  claim 1 , wherein:
 the light-absorbing layer has a binder layer containing at least a metal between the base and the DLC layer. 
 
     
     
       14. The scale according to  claim 1 , wherein:
 the light-absorbing layer has a reflectance no greater than 20% with respect to light falling within the predetermined wavelength range. 
 
     
     
       15. The scale according to  claim 1 , wherein the base is made of one of stainless steel and crystalline glass having an expansion coefficient of substantially zero. 
     
     
       16. The scale according to  claim 1 , wherein the base is made of one of metal, glass and plastic. 
     
     
       17. The scale according to  claim 1 , wherein the base is a metal having a thickness in the range of 0.1 mm to 5 mm. 
     
     
       18. The scale according to  claim 17 , wherein the scale is flexible so as to be capable of being reeled.